This invention relates to a package for use in the microwaving of cookable items, such as popcorn, other food products, or other substances, and more specifically pertains to the easy opening feature of such packages wherein the packages at the top opening are characterized by a peelable seal, which seal is strong enough to maintain the closure as against the heat required for cooking and pressure generated thereby, but which nevertheless is permeable to steam, thus allowing the bag to vent itself, and furthermore, is a sufficiently releasable seal to permit consumers to peel open the package conveniently without exerting undue force.
Another key aspect of prior art microwavable packages, aside from the ventable easy opening closure, is that the package maintains its integrity during filling, storage, distribution and cooking. The package must be sufficiently impervious to cooking oil that it will not weep or bleed oil during a reasonable grocery store shelf life at room temperature, nor during the ensuing cooking and serving usage of the package. The package must not rupture or prematurely open during cooking by virtue of heat and/or pressure in the package during its shelf life. Also, the side and bottom walls of the package, unlike the top closure, must provide a proper barrier against moisture or steam permeation.
Previously, in order to accommodate the broad and comprehensive attributes of a microwavable package, particularly for popcorn, it has been necessary to construct such packages or bags of laminar materials having at least an inner lining or layer and an outer layer for each of the side and bottom walls of said package or bag. The inner layer's fabrication has been restricted to a particular film such as a polyester which is one of the only films commercially available which can withstand the heat of the microwave cooking while also having the tendency to break or peel away at the top during cooking to provide venting and easy opening of the package by the consumer subsequent to cooking.
However, such film materials are characterized by having such low seal strength along the side wall and bottom edges and seals of the package that it has been necessary to reinforce such packages with paper-to-film adhesion in order to prevent bleeding, weeping and other deleterious breakdowns in the package integrity, and to give strength to the package in general. Consumers have even been known to use supplemental wrapping of such bags to prevent moisture permeation and manufacturers have also restricted the types of foods which they package in such easy opening or as sometimes referred to as self-opening style (SOS) microwavable bags.
Various U.S. patents disclosing miscellaneous types of microwavable packages for popcorn and the like which have easy opening features include the following: U.S. Pat. No. 4,571,337; U.S. Pat. No. 2,865,768; U.S. Pat. No. 3,973,045; U.S. Pat. No. 3,052,554; U.S. Pat. No. 4,358,466; U.S. Pat. No. 2,189,174; U.S. Pat. No. 3,851,574; U.S. Pat. No. 4,292,332; U.S. Pat. No. 2,633,284; U.S. Pat. No. 3,478,952; and U.S Pat. No. 3,511,746.
It would therefore represent a substantial advancement in the art if a microwavable bag were provided which would be ventable and easily opened at its top closure without the need for additional structural materials to reinforce the bag against absorption of moisture and/or oil during storage, cooking, subsequent heating and/or distribution or filling of the microwavable bag, and which bag could or would be resistant to other deleterious breakdowns to its structural integrity.